Experimental investigation on the influence of temperature on the fracture surface variations of granite after Brazilian splitting tests

Understanding the variation in the morphology of rock fracture surfaces after high-temperature is of great significance for evaluating the strength, deformation, and seepage characteristics of deep engineering rock masses. In this study, the variations in the granite fracture surface roughness after exposure to different temperatures (25-800 degrees C) were investigated, and the damage deterioration mechanism was revealed. The results showed that the maximum fluctuation (Z) and root mean square of the first derivative (Z2) of the granite fracture surface tended to increase with increasing temperature, whereas the fractal dimension (D) decreased, suggesting that the higher temperature contributed to greater roughness of the fracture surface. The anisotropy of the fracture surface was more evident at higher temperatures and had greater roughness in the 45 degrees-75 degrees, 105 degrees-135 degrees, and 155 degrees-170 degrees directions after different temperatures. Physicochemical reactions, such as dehydration, quartz phase transformation, and mineral oxidation, occurred in the granite owing to high temperatures. These reactions changed the crystalline state of the minerals and facilitated the increase and expansion of microcracks, thereby weakening the cementing property between mineral particles. Fracture surfaces with higher roughness were formed after tensile failure of the rock. The research results may provide theoretical references for the construction and operation of deep engineering.